1. Field of the Invention
The present invention relates to means for correcting the position of the bottom dead center of a slide in a press.
2. Description of the Prior Art
In general, a press shows variations in the bottom dead center position of the slide, when operated at high speeds or continually for a long time. This problem is caused by the fact that when greater inertia force developed by a higher speed operation of the press is applied to the slide, clearance around the crankshaft causes variations in the bottom dead center position of the slide, in spite of balancing the weight of the slide by an air balancer and other suitable means, and that when the operation is continued for a long time, connecting parts such as the plunger connection are expanded by heat generated in the press to cause the bottom dead center of the slide to be lowered and in case the operation is further continued, the frame, especially the column is thermally expanded to cause the bottom dead center to be raised.
To correct these variations in the bottom dead center position of the slide, the prior art has proposed to employ a stopper to limit the bottom dead center position or the operation of the press itself has been stopped severally for accomplishing fine adjustment.
The former prior art, however, causes loss of efficiency of the press, and in case of precision machining, adjustment of the position of the stopper is difficult. The latter prior art has the problem of requiring troublesome work as well as substantial reduction in the working ratio of the press.